O2 sensor on toyota p/u

Hey,
I checked the code for my "check engine lite" and it is 21...the O2 sensor. I was looking to repalce it in my 1990 toyota p/u. its easy enough to get to, but the bolts are a heap of rust. if they break off, is it a major problem? i dont want to open a can of worms, the truck runs good, but the check engine light is on for this reason.
thanks
birch

If it has been replace already then the sensor may screw into the base plate. Look carefully. If not then you have to get those rusty nuts off. Heating with oxy-acetylene torches works wonders, but if you don't have or don't trust yourself I would suggest leaving it to the pros. A new pipe won't be cheap.

I have an Irwin rounded-off bolt remover set, similar to the Craftsman kit
Works wonders (Available at Home Despot)
These being smaller rusted nut the Lisle kit # 19250 Stuck Bolt, Nut & Stud Remover might be a better choice depending on the actual condition, especially if there's not enough rusty nut for the rounded bolt remover to grab onto
The Lisle is available through Sears also

I would have to agree with slickshift. The Irwin Bolt remover kit is awesome. Heat them up, and crank away. As previously noted if you don't feel comfortable with making the repair bring it to the dealer. Hope that helps.

Once you remove an oxygen sensor,the check engine light will come on and stay on even after you have replaced the sensor,you need to get the computer re-set to get the light to go off,or do what I did and cover it with electric tape.